Abstract <p>The mechanism of high-temperature modification of a saponite-containing material, recovered from the return-water suspension during beneficiation of kimberlite ores at the Lomonosov mining and processing plant (MPP) of JSC Severalmaz, was investigated. It was shown that mechanical activation of the concentrated solid phase (saponite content 80%) followed by firing at 900°C leads to formation of the mineral forsterite via an intermediate serpentinization stage of the precipitate. Increasing the powder treatment temperature to 1050°C produces additional synthesis of enstatite. The minerals synthesized during saponite modification are characterized by an increase in energy density. Calculated values of the crystal lattice density parameter for the minerals studied are reported. A functional relationship was obtained for calculating the microhardness of the crystalline structures; the resulting microhardness values increase in the series: saponite, serpentine, enstatite, forsterite. It was found that the coefficients of volumetric thermal expansion of the final modification products (enstatite and forsterite) are practically equal. The microhardness of the minerals’ crystal lattices (the modification products) and their volumetric thermal expansion have a key influence on the properties of the final ceramic products. Mechanical activation of saponite and high-temperature treatment of the resulting powder enable the manufacture of ceramic products from saponite-containing wastes by semi-dry pressing followed by firing. It was established that the fabricated ceramic samples meet the requirements of State standard GOST 13996-2019 with respect to water absorption, flexural strength, and frost resistance.</p>